Move to a protocol-based interface for core

[cmyr]

A refactor that's long overdue: just as we define a client interface in Client.swift, we should define a core interface. All the various core methods would be presented through this interface; behind the surface it would wrap something like the existing CoreConnection class.

This will make it easy for us to change how the core connection is managed at some point in the future, and will also let us write tests in xi-mac that don't need to spin up a real instance of the core.

[jkaan]

@cmyr Hi there! I could pick this one up. Would it for now just involve putting the public interface of the CoreConnection into a protocol and typehinting to that interface instead of the concrete implementation?

[cmyr]

CoreConnection doesn't really have a typed interface at all; it just exposes functions for sending raw arbitrary RPCs. What we'd really like is to have a protocol that describes the legal, existing RPCs, and then implements that for CoreConnection by translating them into the raw RPCs.

We might also consider having a protocol for the CoreView interface, which describes just the RPCs that are scoped to a view.

There is a lot of RPC surface area (especially considering all of the movement commands) so I think it would be okay to go halfway, initially; for instance you could have a protocol method "raw_notification" that still lets you specify a command by it's (string) method name.

edit: hello! 👋

[cmyr]

oh, also: there was an earlier attempt at something like this, in Dispatcher.swift. This predates my involvement in the project, and doesn't seem to have really ever been consistently used; I would expect this new work to also result in us removing that file, I think?

[mmatoszko]

Ok, there are still couple of Events in Dispatcher.swift which should be moved into XiCore protocol:

• Events.Save
• Events.SetLanguage
• Events.StartPlugin
• Events.StopPlugin
• Events.SaveTrace

Every of those require more or less the following steps:

• Adding the method to XiCore
• Implementing it in CoreConnection
• Adding an appropriate test in XiCoreTests
• Using the XiCore method instead of Events.xxx in the code.
• Removing the occurrence of Events.xxx in the Dispatcher.swift

Those can be easily tackled as a separate PR's.
Here's an example which should be super easy to follow: Events.Swift. If you have any questions, just let me know 👍

[cmyr]

closed by #350.